<gm:page title="My App" authenticate="false" onload="init()">

<script>
var selectedOverlay = null;

function init() {
var map = new GMap2(document.getElementById("myMap"));
var geoXml = new GGeoXml("http://mapgadgets.googlepages.com/cta.kml");
map.setCenter(new GLatLng(41.882853, -87.642059), 11);
map.addOverlay(geoXml); 
}
    
</script>

<gm:map id="myMap" style="width: 500px; height: 300px"/>

</gm:page>